As the opening credits role, several motorcycles pull up to a garage, each one painted with a raven sitting on top of a skull, with the word “Expendable” under it. The credits continue to role and it cuts to an oil barge somewhere off the coast of Somalia. Inside, the crew of the ship are being rounded up by Somalian pirates and moved to the ship's main hold.

Just outside the ship, a small black boat approaches carrying a number of heavily armed figures.

The lead pirate (Amin Joseph) starts recording a message for the ship's company/owners. He claims that they have had the hostages for 3 months and the company has yet to pay the ransom of 3 million dollars. To show that they are serious, they will execute some of the crewmembers. Just as the lead pirate is about to disembowel one of the crew, a large black duffel bag drops onto the deck, followed by targeting lasers tracking the pirates  the Expendables have shown up to pay up the ransom and rescue the hostages.

So, the Expendables are:

Barney Ross (Sylvester Stallone)

Lee Christmas (Jason Statham)

Ying Yang (Jet Li)

Gunner Jensen (Dolph Lungren)

Toll Road (Randy Couture)

Hale Cesar (Terry Crews)

The leader of the Expendables, Barney, offers the pirates the 3 million dollars in exchange for the hostages, but the lead pirate demands 5 million. Barney tries to convince him to accept the offer but the situation begins to escalate. Gunner Jenson is just itching to fire but Barney tells him to hold it. The pirate leader has had enough and raises his knife to the hostage, only to be blown clear in half by Jensen's grenade launcher. Huge gunfight ensues and the majority of the pirates are killed. Another standoff happens with the pirate's second in command holding a gun to another hostage. Barney and Christmas have a quiet argument over who can take out the remaining pirates faster (Barney's six-shooter versus Christmas' throwing knives). Everything is at a standstill until Christmas' cell phone goes off and guns start going off again. Barney and Christmas both take down the rest of the pirates, and having a jovial argument over who killed the pirates first.

In the aftermath of the gunfight, Barney spots Jensen on the upper deck, about to hang a pirate because it’s “traditional.” Barney tells him to stop, but Jensen is clearly a bit 'off.' Yang sneaks behind to disarm Jensen, and the two fight. Yang injures Jensen but is pinned again the bulkhead and about to be gutted before Barney holds a gun to Jensen's head and orders him to back down. Jensen eventually relents and gets tied up for the ride home.

On the plane home (the Expendables have their own plane), Christmas talks to Jensen to make sure he's settled down, and frees him.

Back in the United States, Barney returns to the Expendable's garage, watched over by Tool (Mickey Rourke), an ex-mercenary/tattoo-artist. Meanwhile, Christmas goes to visit his girlfriend, Lacey (Charisma Carpenter), only to find that she has left him for someone else. Christmas leaves in anger and returns to the garage. Tool informs them that there are some new jobs coming in, two easy ones, and one that's “from hell and back.”

Cut to a South American island called Vilena, where a militant dictator General Garza (David Zayas) is informed that there are traitors among his workers. Turns out that several workers may or may not have stolen property from him. Before General Garza can interrogate the men further, James Munroe (Eric Roberts) guns down one of the men, and advises the General that it is also “his” property too, and tells him to kill the others to make an example of them.

Cut back to the United States, Barney meets with their next employer, Mr. Church (Bruce Willis). Another potential mercenary shows up too, Trench (Arnold Schwarzenegger) but after a brief description, Trench backs out, as the mission would only be taken by someone who’s crazy.

Barney accepts the challenge, but demands a 5 million dollar fee, with 2.5 million upfront just to scout the place and determine whether the mission is even possible. Mr. Church agrees, but makes it known that he and his people would hunt down Barney and his men if they try to screw them on the deal. Back at the garage, Jensen shows up looking for work, but Barney turns him down, telling him that he can't trust him anymore  Jensen has been going out of control, and possibly on drugs. Jensen warns Barney to be careful, and leaves.

The next scene shows Barney and Christmas packing up and flying their plane, now disguised as a wildlife conservation plane, to the island of Vilena.

Upon arrival, it’s evident that the government/militia has taken over, bossing people around and generally doing the third-world militant dictator stuff one would expect. Barney and Christmas pretend to be ornithologists (scientists studying birds) and use the excuse to secretly take photos of James Munroe and his goons. The duo then meet up with their contact, Sandra (Giselle Itie). Its evident that Sandra isn't the type of person the Expendables generally deal with and Barney is suspicious. Sandra takes them on a driving tour of the island and gives them some background into the political situation on Vilena. Some time over the last year, an American (James Munroe) bought over General Garza and is now using the local farmlands to grow cocaine, using the locals as slave labour, and murdering anyone who gets in the way.

Barney asks Sandra to take them as close as she can to Garza's compound. On their way there, Christmas gets out and sneaks into the forest himself to scout ahead (his speciality) while Barney and Sandra drive the rest of the way there. Outside the perimeters of Garza's compound/base, Barney scouts the terrain and it looks pretty bad  helicopters, machine gun nests, and lots of armed troops everywhere. A truck full of soldiers soon spots them and Sandra tells Barney to keep quiet and let her speak. It becomes evident that the soldiers won't harm Sandra because she is actually Garza's daughter. The lead soldier orders for Sandra to be taken to the General while the others prepare to execute Barney. Out of nowhere, a knife plunges into the soldier and it appears that Christmas has snuck up on them. Barney and Christmas take on the troops and after a bit of knifing, shooting, and bone snapping, all is quiet again.

As they leave, Barney offers to take Sandra away, but she refuses, saying that she must stay with her people and try to fix what’s wrong with Vilena. Barney orders Christmas to take Sandra onto the plane anyway, but Sandra refuses and Christmas has no choice but to leave her. Meanwhile, Barney sneaks to the docks to take out the guards watching their plane. Munroe, his main goon Paine (Steve Austin) and a whole bunch of soldiers (at least 40) arrive and attempt to stop them from escaping. Barney runs after the plane as it speeds up along the docks and barely makes it onto the plane as Christmas flies them out of there.

Both Christmas and Barney make it out of there, but decide to send Munroe a message. Barney turns the plane around while Christmas crawls into the plane's nose cone, which houses a quadruple set of heavy machine guns. They circle back on the island and strafe the dock, hosing down Munroe and his men in a single pass. Barney then hits the plane's fuel dump, pouring airplane fuel all over the dock right before Christmas ignites the whole mess with a flare gun. The entire dock is blasted to hell, with Monroe, Paine, and only a few others surviving the explosion.

Back in the United States, Barney and the others do a bit of research using the photos they took and figure out that Munroe was actually an ex-CIA agent that went rogue and decided to take over the drug operation for himself. Mr. Church is most likely CIA as well, who hired the Expendables because it would look bad for the CIA to attack a South American island. Barney and Tool agree that its suicide and decide to turn down Mr. Church’s job and return the cash.

Christmas returns to apologize for abruptly leaving Lacy, but finds that her new boyfriend has beaten her. Christmas gets her to take her to him, and proceeds to viciously beat up the boyfriend and all his friends. He tells her that this is what he does, and takes her away.

Back in Vilena, Munroe figures out that the Expendables had help in escaping, and believes that its most likely Garza's daughter. He orders Garza to get rid of her, but even Garza is hesitant to kill his own daughter. A moment later, Paine comes in with Jensen, who has now defected from the Expendables.

Some time later, Sandra is capture and brought in for interrogation and torture.

Barney is ok with giving up on the mission, but can't help thinking about Sandra, and about why she would give up on the chance to leave that horrible place. He has a heart to heart talk with Tool, who reveals that after so many missions, and all the fighting and killing, he feels dead inside. Several years back, he had the chance to rescue a young woman from suicide, but didn't, and feels that the last bit of himself had died with her. This spurs Barney into deciding to go save Sandra by himself.

The next day, Barney and Yang head off to Mr. Church to accept the mission, but midway there, Munroe’s men, and Jensen ambush them. After a long car chase, all of Munroe's men are dead, but Barney and Yang crash into a warehouse with Jensen right behind them. Barney is stuck inside his truck, while Yang fights Jensen. Yang is fast, but Jensen is huge. After trading some punches, Yang draws Jensen into a low ceiling area where his height is a disadvantage. Yang takes the opportunity to brutally assault Jensen, but as he gets tired, Jensen replies with “my turn,” and beats the crap out of Yang. Jensen lifts Yang up, preparing to impale him on a broken pipe, but is shot through the chest by Barney.

As Jensen lies on the floor, barely alive and bleeding out, Barney tries to get information on who sent him. Jensen regrets turning on his friends, and tells Barney everything that he learned while working for Munroe (e.g., the layout of the compound, where they store the weapons, weak points, etc.)

Barney preps the plane and prepares to leave for Vilena alone, but sees that the others have already loaded up and prepared to go with him, even if it is a suicide mission. Cesar talks to Road about his favourite weapon, a fully automatic combat shotgun with special explosive ammunition  talking to it like it’s his girlfriend.

The Expendables arrive outside Garza's compound. Barney goes after Sandra while the rest sneak through the compound planting explosives, killing guards, and causing all kinds of havoc. Down in the cellar, Barney reaches Sandra and attempts to get her out, but is attacked by Paine and his men. Barney fights Paine one on one while the rest of the Expendables fight a massive army of Garza's men. While Barney and Paine beat the snot out of each other, the others are pinned down, running out of ammo, and taking a few bullets. As it looks like they're screwed, Cesar shows up with his shotgun and rips apart Garza's men from behind, saving the rest of the team (very brutal scene). In the confusion and gunfire, Paine takes Sandra with him, and escaping with the remaining men.

Paine takes Sandra up to Munroe and Garza. Realizing what his daughter was trying to do, and what he has become due to his greed, Garza finally turns against Munroe, but is shot in the back while trying to rally his men. Munroe sees that there is no point in staying and decides to escape to the waiting helicopter, taking Sandra along as insurance.

Downstairs, The Expendables are pinned behind a brick wall, surrounded by the rest of militia. Barney waits for Sandra to clear the building, then triggers all the explosives that have been placed all over the compound. The building is blasted to hell and in the confusion of the explosion, the militia is taken by surprise and the Expendables charge towards the main base, fighting and killing along the way.

Barney and Christmas shoot and knife their way through the bulk of the troops while Yang blows up every building/tent/vehicle he can find, and Cesar destroys all the guard towers with his gun. Paine helps Munroe escape the base, but is confronted by Road. The two have a brutal fight and Paine is eventually knocked into a fire and immolated.

Munroe and Sandra are about to reach the helicopter and it looks like Barney can't get there in time, but in a last ditch attempt to stop Munroe, he and Cesar throw an artillery shell at the helicopter and Barney shoots it, destroying Munroe's only means of escape.

Munroe heads towards the forest, still holding Sandra hostage. Barney shows up, but is forced to lower his gun when Munroe points his gun at Sandra. Munroe shoots Barney, but doesn't kill him (bullet-proof vest). Sandra fights back and while Munroe is distracted, Barney whips out his six-shooter and fires at Munroe, and at the same time, a large knife goes through Munroe's chest  Christmas had snuck behind and was waiting for the chance to strike.

With Munroe dead, Barney and Sandra embrace. The next day, Barney gives his share of the money to Sandra to help her rebuild Vilena, and leaves to return to the US. Back at the garage, the team celebrate, along with Jensen, who had survived the bullet wound, and rejoined the team.

The movie ends with the Expendables riding off into the city on their motorcycles.